This might be too late, but Sparano + Mooney does pretty good work, Anne Mooney is a professor at the University of Utah and so I think she has more ideas than what seems to get passed around the Salt Lake architectural community. I would say they are the most cutting edge, and probably your best bet. Prescott Muir is considered one of the best in the area, but I don't know how cutting edge he is, but he at least has ability. He worked on the UMFA with Machado + Silvetti, but he also has done box stores (but hey, we all have to pay the bills) Other than that, I can't think of any, if you look at all the best buildings in Salt Lake, most of them are imports. Cutting edge is not something Salt Lake is any good at